Place: 3F Bldg 3, KEK
Time:  10:30, 98/05/29

[0] Agenda
   
   0.1) General Notifications
   0.2) CDC R&D Status (Part II)
   
[1] General Notifications

[1-1] ACFA News Update (T.Matsui)

   T.Matsui will visit IHEP, Tsinghua Univ. in China
   as a delegate in the period of June 10-13.
   
   A new PC on which the ACFA server resides will arrive
   on June 1 and will be set up by H.Sendai soon after.

[1-2] KEKVAX (A.Miyamoto)

   KEKVAX will be shut down in December.

   
[2] CDC R&D Status Part II (H.Kuroiwa)

   H.Kuroiwa made a interim report on his analysis results from
   the beam test at the Tanashi branch.
   
   Items to study with the beam test data include:
   
   (1) chamber signal properties as a function of
       	drift length
       	incident angles (theta, phi)
       	pulse height
       	
   (2) performance
   	spatial resolution
   	efficiency
   	2-track separation
   
   H.Kuroiwa is now concentrating on single-track data to attack
   item (1). It was pointed out that there is often a trailing pulse,
   which is smaller in size and width. The probability to get the
   trailing pulses increases with the incident angles. So far he
   found:
   
   (i)  no correlation in pulse height between a main and its 
        trailing pulses.
   (ii) trailing pulses, if there are more than one, have similar
        shape and size.
   (iii) the shape, not only the size, of the main pulse depends
         on both theta and phi. 
   (iv) the arrival time difference between the main and the second
        pulses clearly depends on phi (the angle in the plane 
        perpendicular to anode wires) but not that clearly on theta.
   (v)  The trailing pulses were not observed for an X-ray source
        but were there for a beta-ray source.
   
   The trailing pulses seem to be originating from real ionization
   clusters in the presence of space charge effects due to the low
   diffusion nature of CO2-Isobutane. More studies are needed,
   though, to draw any solid conclusion.